The present invention relates to a sealing arrangement, including a slide ring seal means, and a counter ring that is accommodated in a holder means that is provided with a presser sleeve via which in an installed state, the sealing arrangement is seated with a press fit on a component that is to be sealed, especially a pump shaft.
Known sealing arrangements of this type serve to seal off pump shafts. Such sealing arrangements have a slide ring seal means with a housing, and a counter ring with a holder means. The slide surface of the slide ring and the slide surface of the counter ring are held in sealing contact by means of a compression spring. The slide ring and the housing are inserted into a pump housing, while the holder means of the counter ring is seated upon the pump shaft via a tubular holder (presser sleeve).
In the non-installed state of the sealing arrangement the slide ring seal means and the counter ring are interconnected by the metallic holder means, with the housing of the holder means, starting from an inner bore of the holder means, extending entirely or partially behind the counter ring and the slide ring seal means in order in this manner to prevent the counter ring and slide ring seal means from coming apart in the effective direction of the compression spring.
When the sealing arrangement is installed, the counter ring holder means is pressed upon the pump shaft, so that during operation the holder means and the counter ring rotate along with the pump shaft. In order during operation of the pump to prevent the medium that is to be sealed from escaping through a sealing gap between the slide surfaces of the slide ring and the counter ring, the front movement deviation of the slide surface of the counter ring must be as small as possible. For coolant pumps of motor vehicles, this deviation is a maximum of 0.1 mm. However, such a small front movement deviation can be maintained only at great manufacturing and control expense, because in so doing not only does the front movement deviation of a radially directed inner wall of the holder means relative to the inner bore thereof play a role, but also the parallelism deviation of the boundary surfaces of an outer holding sleeve as well as the slide surface and the backside of the counter ring play a role. Added to this can also be errors in positioning that occur when the counter ring and outer holding sleeve are pressed into the holder means.
In the installed state, the slide ring seal means is pressed into a receiving bore of the pump housing. During installation, the counter ring holder means is pressed by a non-illustrated tool onto the pump shaft, and is so doing is pressed against the slide ring seal means until an operating length is achieved at which a conically widened portion of the holder means has assumed a certain distance from the housing of the slide ring seal. This distance is necessary in order to achieve a freedom of rotation between the holder means and the slide ring seal means. Due to the metallic counter ring holder means, the position of the counter ring upon the pump shaft is fixed by the metallic press fit and not by axial support via a fan wheel. Rather, between the fan wheel and the holder means there is a gap that precludes contact between the fan wheel and the holder means. The working length is therefore affected merely by the precision of the press-in tool and not by the position of the fan wheel upon the shaft.
The frictional connection produced by the press fit between the holder means and the shaft must be great enough that not only a shifting of the holder means on the shaft due to the force of the compression spring and due to the force that acts in the direction of the slide ring seal means from the hydraulic pressure of the medium that is to be sealed but also a twisting of the holder means relative to the shaft due to the frictional moment resulting in the sealing gap, are reliably prevented. To reliably transfer the forces or frictional moment, a relatively short press fit in the axial direction would suffice, since the forces and the moment are relatively low. However, the press fit connection between the holder means and the shaft must in addition be medium-tight in order to prevent the medium that is to be sealed from escaping between the holder means and the shaft. For this reason, the press fit length is in practice relatively long, especially since with metallic press fits, the formation of roughness and hence leakage areas at both joint surfaces cannot be reliably precluded. In order to prevent leakage areas between the two joint surfaces, it is additionally necessary to set at the inner bore of the holder means very high requirements with regard to diameter tolerance, concentricity deviation, cylinder shape deviation, and surface quality. These requirements can be fulfilled only at high manufacturing and control expense.
A further drawback of the heretofore known sealing arrangements consists in that the conically widened portion of the holder means must have a greater outer diameter than the inside diameter of the slide ring seal means in order in a non-installed state of the sealing arrangement to prevent a separation of the holder means from the slide ring seal means. The result is that the widened portion can only be produced in an additional step after the holder means and the slide ring seal means have been joined together. This has the further drawback that during provision of the widened portion, the inner bore of the holder means can be deformed to an unacceptable extent. Finally, the heretofore known sealing arrangements cannot be removed, for example for inspection purposes, without destroying the holder means, since for this purpose the widened portion must be returned to its original shape.
It is therefore an object of the present invention to provide a sealing arrangement of the aforementioned general type that has an increased functional reliability while at the same time having reduced manufacturing and control costs.